1. Technical Field
The present invention is directed toward a guide for bicycle cables, and more particularly toward a low-friction derailleur cable router.
2. Background Art
Bicycle drive systems have been under constant redesign and refinement since bicycles were introduced over one hundred years ago. It is now common-place to have bicycles having between 1 and 24 "gears" or "speeds" allowing a bicyclist to select an appropriate gear as riding conditions change. A typical prior art rear wheel drive system is illustrated in FIG. 1. A rear wheel 10 is mounted to a rear drop out 12 of a bicycle frame by means of an axle 14. A hub 16 contains ball bearings or the like for providing smooth low-friction rotation of the wheel 10 about the axle 14. Adjacent the hub 16 is a rear cluster 18 which contains a plurality of sprockets 20 of increasing diameter. A chain 22 engages a select sprocket 20 and the chain 22 can be moved between the sprockets by actuation of the rear derailleur 24. The rear derailleur 24 is actuated by changing the tension in the derailleur cable 26 by movement of a shifter (not shown) mounted to the bicycle frame forward of the rear derailleur 24 connected to a distal end of the derailleur cable 26. As is appreciated by almost all bicycle users, the smaller the sprockets 20 engaged by the chain 22, the greater the amount of rotation of the wheel 10 for a given distance of chain movement.
A typical rear derailleur 24 as illustrated in FIG. 1 includes an actuator arm 28 to which the derailleur cable 26 is fixedly attached at its proximal end by means of a clamp 30 or other connecting structure. Most rear derailleurs in use today are "rear fed", meaning that the derailleur cable 26 is fed to a derailleur 24 from the rear, as is illustrated in FIG. 1. Thus, a derailleur cable feed 32 receives the cable 26 from the rear of the derailleur. In order to facilitate the change of direction of the derailleur cable 26 from a forward portion of the bicycle to the rear of the bicycle, a flexible coupling or cable housing 34 is provided between the derailleur cable feed 32 and a stop 36 or other apparatus fixed to the bicycle frame. The cable housing 34 is flexible laterally but ridged axially. It therefore maintains the length of cable running inside of the cable housing 34. A barrel tension adjuster 36 may be provided between one end of the cable housing 34 and the derailleur cable feed 32 for increasing or decreasing the effective length of the cable 26 to adjust the rear derailleur 24.
Most rear derailleurs on the market and in use today are rear fed derailleurs. In addition, the use of the cable housing 34 to direct the derailleur cable 26 to the rear of the rear derailleur 24 is virtually exclusive. While the cable housing 34 has proven to be effective at routing the derailleur cable 26 in this manner, it is not without some serious drawbacks. First, as illustrated in FIG. 1 the cable housing 34 forms a rather large loop extending above and behind the rear derailleur 24. This loop is unsightly and gives a bicycle a decidedly "clunky" or "low-tech" appearance. In addition, the loop formed by the cable housing 34 often becomes tangled with or snagged with obstructions during handling and riding of a bicycle. This problem is particularly acute where the bike is used for off-road applications such as mountain biking. Furthermore, even for non-off-road applications such as road racing the loop 34 provides undesirable wind drag. The cable housing 34 is also a source of considerable friction on the derailleur cable 26. This friction increases markedly as the bike is ridden over time and dust and grit work their way inside the housing 34. Also, as the loop is made larger increased force is required to move the cable 26. This increased force is due to the longer friction causing surface and the fact that the resulting force applied by the derailleur cable 26 to the derailleur actuator arm 28 is dissipated by the derailleur cable 26 being directed over a wider arc.
The present invention is directed toward overcoming one or more of the problems stemming from the use of the cable housing to route a derailleur cable to a rear-fed rear derailleur.